Manual pellet loader for Boschman automolds

ABSTRACT

A manual loader for use in bypassing an automatic pellet feeder for an automold machine used to encapsulate integrated circuit assemblies in plastic. The loader has a support mounted adjacent the mold section of the machine. The loader also has at least one pellet boat which moves relative to the support into and out of said mold section. The pellet boat includes one or more pellet pots which are adapted to receive and hold a solid pellet of material. The loader has a release mechanism which is movable between a blocking position and a release position. The release mechanism retains the pellets in the pellet pots in the blocking position and releases the pellets from the pots when manipulated to the release position for dropping the pellets into a mold of the machine&#39;s mold section.

TECHNICAL FIELD OF THE INVENTION

The present invention relates generally to encapsulating electronicelements in a plastic material, and in particular the present inventionrelates to an apparatus and method for bypassing the molding machineautomatic delivery system.

BACKGROUND OF THE INVENTION

The Boschman automold machine is utilized to encapsulate electroniccomponents such as integrated circuits in a plastic material. Circuitdies are fabricated or die cut from wafer material and then added to asubstrate material forming a circuit sub-assembly. The circuitsub-assemblies are run through the Boschman machine to encapsulate theparts in plastic to protect the circuits dies and leads or wire bondsfrom damage.

The Boschman machine operates in a manner where the circuitsub-assemblies are automatically fed into the mold section of themachine with one sub-assembly disposed in each mold cavity. Plasticmaterial is then injected through a sprue into the mold cavities toencapsulate the subassemblies. The encapsulated components are thenautomatically ejected or unloaded from the machine. The plastic materialis initially provided in the form of a pill or pellet and may consist ofany number of materials such as a thermoset resin or a melamine compoundor the like. The pellets are automatically transported by a pellet boatwhich individually delivers a pellet to a pot adjacent each mold cavity.The mold section is heated to liquefy the pellets prior to injection ofthe plastic material into the mold cavities.

The mold cavities and material transport passages of the automoldmachine must be cleaned periodically to remove excess material andcontaminants. The automold machine runs on a continuous cycle orprocess.

One method of cleaning requires the machine to be shut down long enoughfor a technician to remove the mold from the machine, replace the moldwith a spare, and restart the machine. This process requires significantdown time for the machine, which is on the order of 60 minutes for eachcleaning cycle. This method requires having a spare mold, which is anadded expense. Further, the removed mold must also be cleaned, addingtime to the cleaning cycle.

An additional method of cleaning may be performed by running cleaningpellets directly through the machine through the production processpath. One problem with this method is that the cleaning pellets areoften of a different size than the plastic material pellets. To run acontinuous line, the system can only handle one size pellet andtherefore the machine must be shut down to convert the system to acceptthe odd size cleaning pellets. Another problem with this method is thatthe machine must be completely evacuated of process pellets beforeloading the cleaning tablets or pellets into the automatic feed systemto avoid mixing of materials. The cleaning pellets leave a residuethroughout the process path and handling system if run through themachine in this manner. One or more cleaning pellets may even be left inthe system when converted over to the process pellets. This causescleaning material to mix with the plastic material contaminating anyparts encapsulated with the mixed materials. The procedure necessary toready the mold for the cleaning process and production processes aredifferent. If the set-up for the production process is not doneperfectly after the cleaning process is complete, the mold must bere-conditioned causing further downtime of the automold machine.

An additional problem with the present machine is that it is difficultand time consuming to do a test or experimental run for materials otherthan the production pellet material. This is because, again, the machinemust be shut down and evacuated of all production pellet material priorto performing the test. Once a test is completed, the machine must againbe shut down for conversion back to production material. Because themachine must be shut down, it would be very time inefficient andtherefore undesireable to attempt to run a low volume test, such as asingle shot test.

For the reasons stated above, and for other reasons stated below whichwill become apparent to those skilled in the art upon reading andunderstanding the present specification, there is a need in the art foran improved apparatus for and method of cleaning a Boschman automoldmachine which results in a more reliable production mold process,requires less machine downtime, and is easier to perform thanconventional known methods.

SUMMARY OF THE INVENTION

The above-mentioned problems with present automold technology and otherproblems are addressed by the present invention and which will beunderstood by reading and studying the following specification. Anapparatus and method of bypassing the automatic feeding system of aBoschman automold machine is described which is useful in the process ofencapsulating electronic components and the like with a plastic materialwhich results in a more reliable product while taking less time toperform.

In particular, one embodiment of the present invention describes amanual loader for use in bypassing the automatic pellet feeder of themachine used to encapsulate integrated circuit assemblies in plastic.The loader has a support mounted adjacent the mold section of themachine. The loader also has at least one pellet boat which movesrelative to the support into and out of said mold section. The pelletboat includes one or more pellet pots which are adapted to receive andhold a solid pellet of material.

The loader also has a release mechanism which is movable between ablocking position and a release position. The release mechanism retainsthe pellets in the pellet pots in the blocking position and releases thepellets from the pots when manipulated to the release position fordropping the pellets into a mold of the machine's mold section.

The manual loader may be used to bypass the automatic feeder system topermit cleaning and experimental testing of mold compounds withoutrequiring a total evacuation of production pellet materials from thefeeder system. An operator need only momentarily stop the machine'sfeeder, load cleaning or test pellets into the pellet boat, maneuver theboat into the mold section of the machine, release the pellets into themold, and remove the boat from the mold section. The operator then needonly run the mold through a single cycle to either clean the molds or toproduce a single shot of experimental integrated circuit assemblies.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of a conventional Boschman automold machine wherethe front cover panels have been removed to view the internal componentsof the machine;

FIG. 2 is a perspective view of the automatic feeder system majorcomponents of the machine of FIG. 1;

FIG. 3 is an exploded perspective view of an upper and a lower moldsection of the machine of FIG. 1 shown with a manual bypass loaderconstructed in accordance with one embodiment of the invention;

FIG. 4 is a side view in cross section taken along line 4--4 of FIG. 4of the manual pellet boat;

FIG. 5 is an end view in cross section taken along line 5--5 of FIG. 4of the manual pellet boat;

FIG. 6 is a top view in cross section taken along line 6--6 of FIG. 5 ofthe manual pellet boat; and

FIG. 7 is a top view of the release shaft in the release position withinthe pellet boats of the manual bypass loader of FIG. 3.

DETAILED DESCRIPTION OF THE INVENTION

In the following detailed description of the preferred embodiments,reference is made to the accompanying drawings which form a part hereof,and in which is shown by way of illustration specific preferredembodiments in which the inventions may be practiced. These embodimentsare described in sufficient detail to enable those skilled in the art topractice the invention, and it is to be understood that otherembodiments may be utilized and that logical, mechanical and electricalchanges may be made without departing from the spirit and scope of thepresent inventions. The following detailed description is, therefore,not to be taken in a limiting sense, and the scope of the presentinventions is defined only by the appended claims.

Referring now to the drawings, FIG. 1 illustrates a Boschman automoldmachine 20 used to encapsulate integrated circuit assemblies with aplastic material as is known in the art. Machine 20 is illustrated inFIG. 1 with the front covers taken off to illustrate the generalinternal components and sections of the machine. Machine 20 includes acontrol unit 21 for programming and setting up the machine to controlthe various steps of the encapsulation process. The control unit 21 maybe programmed to accommodate many different applications. The machinealso includes a feeder system 22 having a pellet supply 24 for holding aplurality of material pellets therein to be used during the process.Below the pellet supply is a pellet separator 26 for separating out eachindividual material pellet for delivery to a pellet transport 28. Theindividual material pellets are fed through the above-describedautomatic feeder system 22 to the mold section 29 of the machine where asingle individual pellet is delivered to each pellet pot as will bedescribed herein.

A mold drive system 34 is driven to bring the two halves of a mold 30together to encapsulate the integrated circuits held therein. A plunger32 is driven into mold 30 to transfer material from a pellet pot throughsprues (not shown) and in to the individual cavities (FIG. 3). Themachine 20 will not be described in any greater detail herein as themachine is well known in the art and the basic process of encapsulatingintegrated circuits by use of the machine is also known in the art. Theinvention is directed to a method and apparatus for circumventing orbypassing the automatic feeder system 22 for cleaning the mold section29 and for easily performing experimental trial molds without having toempty out or clean the automatic feeder system.

Therefore, FIG. 2 illustrates the basic components of the automaticfeeder system 22 in greater detail. Pellet supply 24 of the systemtypically includes a pair of containers 40 which are each filled with aplurality of material pellets 42 so that a continuous supply of pelletsmay be provided to the system. One container 40 may be removed from thesystem and refilled while the other one remains attached to the systemto continuously supply material pellets. A spiral wall 43 urges pellets42 within each container 40 toward one end so that they may be droppeddown a chute 44 to a rotating cage 46 which separates and properlyorients the material pellets 42 therein. The pellets 42 are transportedby a small conveying system 48 to the pellet separator 26 where thepellets are individually dropped into a pellet boat 50. The pellet boat50 transports the pellets to the mold section 29 of the machine forfurther processing steps.

A lower mold 60 and an upper mold 61 of the mold section is illustratedin FIG. 3. The exemplary lower mold 60 includes two parallel moldcavities therein, each having a plurality of spaced-apart pellet pots62. A number of circuit cavities 64 are adjacent each pellet pot 62. Anintegrated circuit assembly (not shown) is held within each circuitcavity 64. The mold is heated so that the pellets within cavities 62turn to liquid. The liquid is injected by the plunger 32 from the pelletpots 62 through the mold channels 66 to the circuit cavities 64. Themold 60 rests against a bottom heater block 70 for heating the lowermold 60. Similarly, the upper mold 61 having corresponding cavities anda corresponding heater block 76 would mate against lower mold 60 duringthe encapsulation process.

During standard operation, the pellet boat 50 is automaticallymanipulated into mold section 29 through upper heater block 76 andfurther manipulated to drop a material pellet 42 into each pellet cavity62. The boat 50 is then automatically moved out of the mold sectionprior to the plunger 32 and mold drive system 34 dropping the upper halfof the mold against lower mold 60.

A typical mold of the Boschman automold machine 20 must typically becleaned about every 600 to 1,000 shots. A mold is typically cleanedoff-line, requiring that each mold be removed from the machine andmanually cleaned by one of several known processes using any one of manysolvents or compounds. Each time a mold is cleaned, the machine must beshut down or paused while the mold is removed. The machine must eithersit idle while the mold is cleaned and replaced or a spare mold must bepre-heated and installed and then the machine must be restarted whilethe primary mold is cleaned. Either way, the machine is down for aminimum of about sixty minutes to swap molds or longer to clean the onlymold. In addition, a qualified technician is required to tear down themold and then re-install the primary mold.

One problem with the present process is that to maximize the up time ofthe machine, two molds must be in existence, adding significant cost toa particular application. Also, the machine and the molds suffer wearand tear each time they are removed, cooled, cleaned, re-heated andreplaced. Additionally, time and productivity are lost each time themachine is down for cleaning. Further, by constantly removing andreplacing the molds, mold alignment is constantly being alteredresulting in inconsistent or flawed component production.

An additional problem which exists with the present Boschman automoldmachine 20 is that it limits or inhibits experimental runs. It is oftennecessary to test new compounds for encapsulating integrated circuits,and to do so using the present machine is difficult, time consuming andmay damage the machine or production run components after anexperimentation run. This is because each time an experimental run isperformed, the machine must be shut down, the feeder system and moldsmust be evacuated of all production pellet material, and then the feedersystem must be filled with the experimental compound.

After an experimental run is performed, the machine must again be downto be evacuated of any experimental compound. Significant time is lostwhen undergoing such a procedure. Also, if the machine is not completelycleared out before and after the experimental run, a mix of materials orcompounds may result, either negating the results of an experimentaltest or producing flawed or damaged production components. Additionally,because of the time it takes to change the machine over, it isinefficient to run a short, very low volume experimental run. It isdesirable that there be a means to bypass the automatic feeder systemwhich would permit an experimental run of even a single mold shot.

It is an object of the present invention to provide a manual loaderwhich bypasses the machine's automatic feeding system, permitting themolds to be cleaned while installed in the machine without causingsignificant production down time. It is also an object of the inventionpermit experimentation without having to clear out the feeder system ofproduction materials or pellets.

FIG. 3 illustrates a manual bypass loader 100 constructed in accordancewith one embodiment of the present invention. Loader 100 is intended tobe mounted within mold section 29 of machine 20 adjacent mold 30 (seeFIG. 1) so that it may be inserted into the mold section from theopposite side relative to the automatic pellet transport or pellet boat50. Bypass loader 100 includes a support bracket 102 mounted to a fixedportion of machine 20 such as a cross member 104 within the mold.

Bypass loader 100 includes a pair of manual pellet boats 106 having aplurality of pellet pots or cavities 108 formed therein which areintended to correspond to pots or cavities 62 in the mold 30 asillustrated by lower mold 60. Bypass loader 100 also includes a splinedshaft or raceway 110 mounted at one end to a rod mounting bracket 112supported by an isolation plate 114 adjacent mold 30. The manual pelletboats 106 are carried on a connecting plate or carrier 116 at one endadjacent support bracket 102. Carrier 116 is adapted to be received andslidable along raceway 110 for moving the manual pellet boats into andout of mold section 29 of the machine as will be described herein.

As illustrated in FIGS. 4 and 5, each pellet boat 106 comprises anelongate structure having a plurality of transverse through boresdefining pellet pots 108 at one end and arranged longitudinally alongthe boat 106. As illustrated in FIG. 5, a longitudinal or axial shaftbore 118 is formed along each boat 106 slightly offset from the centralaxis of each pellet boat. The diameter of shaft bore 118 is intended toslightly impinge into each pellet pot 108. A release shaft 120 (shown inFIG. 7) is received in and extends along the shaft bore and includes aplurality of transverse grooves or clearance cutouts 122 which are eachintended to correspond in contour and position with one of pellet pots108.

When the release shaft 120 is in a release position, each clearancecutout 122 aligns with a corresponding pellet pot 108 to provide anunobstructed passage through pellet boat 106 via each pellet pot. Thisallows a material pellet 42 held within each pot to pass directlytherethrough. The release shaft 120 may be manipulated by eitherrotational or longitudinal movement to a blocking position such that theclearance cutouts 122 do not correspond or align with pellet pots 108.In this condition, a portion of the diameter of release shaft 120impedes or impinges upon the perimeter surface of pellet pots 108, thusobstructing passage of material pellets through the pots. Iflongitudinal movement of the shaft is to be used to block passagethrough the pots, the clearance cutouts may alternatively be annularrings or grooves formed around the outer diameter of shaft 120.

Each pellet boat 106 includes a raised section 123 corresponding to theend of shaft 120 including the pellet pots 108. The raised sectionprovides a pellet nest 124 above the blocked portion of the pellet pot.Thus, a pellet 42 may be received in pellet pot 108 and retained withineach pellet nest 124 when shaft 120 is in the blocking position asdescribed above.

To operate bypass loader 100, each release shaft 120 must be in theblocking position prior to inserting material pellets 42 within thepellet pots 108. Once the material pellets are added, a user willmanipulate a handle 130 to slide the bypass loader 100 forward alongraceway 110 until all of the pellet pots 108 pass through isolationplate 114 into the mold section 29. A positive stop mechanism or anelectronic sensing means such as detect rod 132 may be utilized to sensewhen bypass loader 100 is fully inserted into the mold section, ensuringthat each pellet pot 108 are positioned directly over a correspondingmold cavity or pot 62 in the lower mold 60.

The release shafts 120 must be manipulated to the release position,permitting the material pellets 42 to pass through the pellet pots 108and boats 106 into the mold cavities 62. The release shafts 120 arespring loaded, and are automatically released when the bypass loader 100is fully inserted into the mold section. The operator then mustmanipulate handle 130 to slide the pellet boats back out of the moldsection 29 to the rest position. The operator then may run the machinethrough a mold cycle. During the mold cycle, the lower mold closes andmakes contact with the upper mold. Pellets 42 drop into the pots 108,and the plunger forces the melted pellets 42 into the channels 66 to thecircuit cavities 64.

The bypass loader 100 of the invention provides two very importantaspects not provided by the existing automatic feeder system 22 of theBoschman automold machine 20. The manual bypass loader 100 permits themachine and its molds 30 to be cleaned without removing the molds fromthe mold section. Further, this may be done without completelyevacuating the automatic feeder system of any production processmaterial pellets. Also, experimental or test runs may be performed usingdifferent pellet material compounds for as little as one mold shot. Eachtest cycle may also include as few as one test pellet or as manymaterial pellets 42 as can be held in the manual pellet boats 106. Thisagain may be done without the necessity of completely evacuating theautomatic feeder system of other pellet material compounds. Successivetest runs may also be run where each run includes a different materialcompound.

To clean the molds utilizing the manual bypass loader of the presentinvention, an operator need only insert cleaning pellets into pelletpots 108 of the pellet boats 106 prior to moving the bypass loaderforward into the molds 30 of the machine 20. The cleaning pellets arethen dropped into the pellet pots 108 of the upper mold 61. This allowsthe cleaning material of the pellets to be heated and injected throughchannel 66 and to the mold cavity 64 to clean them. The cleaningmaterial is then removed from the mold cavity 64, which can occur eithermanually or automatically. However, since the cleaning material tends tobe more fragile, the cleaning material is preferably removed by hand.

To run an experimental test, the automatic feeding system is simply shutoff and experimental material pellets are inserted into pellet pots 108of manual pellet boats 106 and then inserted into the pellet cavities 62in lower mold 60 as described above. The experimental material will thenbe heated by the molds, allowing it to flow into circuit cavity 64 toencapsulate integrated circuit assemblies with the experimentalcompound. The operator then cycles the machine to eject them from thecircuit mold cavities and removes them from the machine in aconventional manner. During experiment or cleaning cycles, lead stripswithout dies are used in the machine 20 for encapsulation, and then arelater discarded. To proceed with a production run from either a cleaningor an experimental cycle, the automatic feeding system may simply beturned back on, permitting the production material compound pellets todrop one by one into the production automatic pellet boat feeders 50.

Although specific embodiments have been illustrated and describedherein, it will be appreciated by those of ordinary skill in the artthat any arrangement which is calculated to achieve the same purpose maybe substituted for the specific embodiment shown. This application isintended to cover any adaptations or variations of the presentinvention. Therefore, it is manifestly intended that this invention belimited only by the claims and the equivalents thereof.

What is claimed is:
 1. An apparatus for use in bypassing an automaticfeeder system of a machine having a mold section for encapsulatingelectronic components, said apparatus comprising:a support adapted tomount said apparatus to said machine; at least one pellet boat movablerelative to said support into and out of said mold section of saidmachine, said pellet boat having a plurality of pellet pots forretaining and releasing material pellets; a release mechanism associatedwith said pellet boat having an elongate release shaft received in anelongate bore formed longitudinally along said pellet boat, said releaseshaft having a plurality of cutouts formed on its outer diameter so thatone of said cutouts corresponds with each one of said plurality ofpellet pots, said release mechanism being movable between a blockingposition and a release position; and wherein said release mechanismretains said material pellets in said pellet boat when in said blockingposition and releases said material pellets from said pellet boat whenin said release position.
 2. The apparatus of claim 1 wherein saidplurality of pellet pots each are a bore formed through said pelletboat.
 3. The apparatus of claim 2, wherein said bores each formedtransversely through said pellet boat.
 4. An apparatus for use inbypassing an automatic feeder system of a machine having a mold sectionfor encapsulating electronic components, said apparatus comprising:asupport adapted to mount said apparatus to said machine: at least onepellet boat movable relative to said support into and out of said moldsection of said machine, said pellet boat for retaining and releasingmaterial pellets; a release mechanism associated with said pellet boat,said release mechanism being movable between a blocking position and arelease position; wherein said release mechanism retains said materialpellets in said pellet boat when in said blocking position and releasessaid material pellets from said pellet boat when in said releaseposition wherein each of said at least one pellet boat further comprisesa plurality of pellet pots adapted for receiving a material pellettherein and releasing a material pellet therefrom; and wherein saidrelease mechanism comprises an elongate release shaft received in anelongate bore formed longitudinally along said pellet boat, said releaseshaft having a plurality of cutouts formed on its outer diameter so thatone of said cutouts corresponds with each one of said plurality ofpellet pots.
 5. The apparatus of claim 4 wherein each one of saidplurality of cutouts aligns with one of said plurality of pellet pots topermit unobstructed passage through said pellet pots of said materialpellets when said release shaft is in said release position.
 6. Theapparatus of claim 4 wherein said cutouts do not align with said pelletpots and said outer diameter of said release shaft impinges into saidpellet pots to obstruct passage therethrough of said material pelletswhen said release shaft is in said blocking position.
 7. The apparatusof claim 1, wherein the release mechanism is automatically placed in therelease position upon insertion of the pellet boat in to the moldsection.
 8. The apparatus of claim 1 further comprising a pair of saidpellet boats.
 9. The apparatus of claim 8 further comprising a carriersupporting said pellet boats, wherein said carrier is slidable relativeto said support.
 10. The apparatus of claim 1 further comprising asplined raceway affixed to said support, said carrier being slidablyreceived on said raceway such that said pellet boat is movable into andout of said mold section.
 11. The apparatus of claim 10 furthercomprising a handle for manually moving said carrier along said raceway.